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working-effectively-with-legacy-code

Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.

Published by ciembor ↗ciembor/agent-rules-books

Try your first task

Find a safe seam in legacy code

Start a fresh conversation.

Use the working-effectively-with-legacy-code skill to inspect <path-to-legacy-code>. Suggest one characterization test that captures current behavior and identify one seam or dependency-breaking step that would make the intended change safer. Limit the result to a small first step and do not modify files yet.

Required inputs

  • Path to the legacy code
  • Brief description of the intended change or risky behavior

Suggested template by Skill Leaderboard, grounded in the linked source. Task evidence ↗

SKILL.md

name: working-effectively-with-legacy-codedescription: Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.license: MIT

Working Effectively with Legacy Code Skill

Use this skill when a task involves risky legacy changes, missing tests, characterization tests, seams, dependency breaking, sprout method, wrap method, or incremental risk reduction.

Before making design or code decisions, read and apply working-effectively-with-legacy-code.mini.md. Use working-effectively-with-legacy-code.md only as a deeper reference when the mini rules are not enough for the current legacy-code tradeoff.